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Ausmoo2

WRX phantom RPM limit problem

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I've been having some issues with the RPM limit on my 2004 sti running a g4 V7-9 ecu.

The car will sometimes rev all the way out to the 7800 limit, but most of the time when it hits a wall anywhere between 5000 and 6500 rpm and the ecu is telling me that the RPM limit has been activated . When I check the logs the times when it hits this "RPM limit" the RPM is jumping up to 18000+ RPM.

This won't happen at the same RPM every time or in the same gear. For example 2nd gear will have no issues and then 3rd gear it will hit this "limit" and other times it will do it in 2nd but not 3rd.

I've tried replacing the Crank angle sensor as well as the Cam angle sensor, but neither have made a difference. 

Any help would be much appreciated. 

Thank you

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It is likely getting noise on the trigger signals so could be a coil breaking down causing noise and then the RPM error.

I'm assuming this is an older install and it has developed over time.

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Hi Simon, thanks for your reply.

Yes, the ecu was installed about 4 years ago before I purchased the car.

The problems only started occuring after I installed a new engine. Would you suggest replacing the coils?

Thanks

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Another thing you can try is set the trig2 lockout to below the point where your trigger issue often occurs.  The ecu will then ignore the cam sensor above this RPM, if the error is related to the cam sensor or cam timing etc that may help.

evTtDw3.png

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Quick update:

Changing coil packs hasn't made any difference, but changing the rpm lockout seems to have fixed the issue. 

Should I leave the lockout at 4000rpm or continue trying to chase down any noise on the sensor? If so what would be the best way to find it?

Thanks

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I dont think there is any harm in leaving the lockout at 4000.  If you wanted to diagnose further, really the next step would be to get an oscilloscope capture of the crank and cam at idle and say 5000RPM, that would usually give you some good clues where the issue is coming from.  It could be something as simple as the cam timing moves slightly out of the allowable range at high RPM for example - I have seen this before with engines that have been "decked" significantly or have mismatched heads/cases.    

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